Tung oil

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Tung oil
Ripe fruit of the tung oil tree (Vernicia fordii).
Raw material plant (noun)

Vernicia fordii , practically identical to Vernicia montana ; also from Vernicia cordata

origin

Seeds

colour

amber (light tung oil);
dark brown (black tung oil)

ingredients
Oleic acid 4-18%
Linoleic acid 4-15%
Linolenic acid 1-3%
Palmitic acid 2-5%
More fatty acids α - eleostearic acid 57–88%, stearic acid 1–3%
Other ingredients Tocopherol up to 1500 mg / kg, tannins , phytosterols , saponins
properties
density 0.936-0.945 kg / l at 15 ° C
viscosity = 113 mm 2 / s at 40 ° C
Melting point 2-3 ° C (fresh oil);
−17 ° C to −21 ° C (briefly heated oil)
Iodine number 147–211 (Wijs)
Saponification number 187-197
Manufacturing and Consumption
Production worldwide approx. 75,000 tons (2004)
Most important production countries China, Argentina , Paraguay
use Pharmacy, medicine, technology, industry

Tung oil , also called Chinese wood oil or elaeococca oil , is a vegetable oil made from the oil-rich seeds of various South Asian tree-shaped species of the genus Vernicia .

Occurrence and manufacture

In China , the tung or abrasin tree ( Vernicia montana ) (also specifically as abrasin oil) and the tung oil tree ( Vernicia fordii ) are used, in Japan Vernicia cordata (Japanese wood oil). The oil from the related light walnut tree ( Aleurites moluccana ) is known as kukui nut oil , and the oils from Reutealis trisperma (bagilumbang oil) are similar . It is obtained either cold or hot pressed from the seeds.

A similar oil, Oiticica oil, comes from Licania rigida , and one is also obtained from Garcia nutans .

Properties and composition

General chemical structure of oils such as tung oil. R 1 , R 2 and R 3 therein are alkyl radicals or alkenyl radicals with a mostly odd number of carbon atoms. Like other natural oils, tung oil is a mixture of triesters of glycerine .

Fresh tung oil is clear, amber-colored, odorless and tasteless (cold-pressed; "white tung oil" ) to dark brown with a fecal odor (hot-pressed; "black tung oil" ) and is comparatively thick. The smell of the light tung oil changes after a while, it then resembles that of rancid bacon , lard oil and is therefore very characteristic and unpleasant.

Tung oil differs from other vegetable oils in its special chemical composition: it consists of up to 80% glycerides from α - elaeostearic acid , a tri - unsaturated fatty acid . It also contains oleic acid residues , palmitic acid residues and stearic acid residues - each bound as glycerine ester. Due to the low proportions of the di- and triterpene esters contained in all milkweed plants , tung oil is not suitable for consumption. The press cake after the oil is extracted is a good fertilizer, but not suitable as animal feed.

Tung oil also has a very characteristic behavior when heated, which plays a role in the technical properties: If it is heated strongly, this results in a strong increase in viscosity , which leads to gelatinization. The specific weight increases while the refractive index is reduced.

Tung oil has been used as a water repellent oil for centuries because it penetrates very deeply and even into the densest wood. Compared to most other oxidative oils, it forms a fine, permanent film that retains its elasticity and moves with the wood.

Extraction

The oil is obtained by pressing the seeds in the ripe fruits, which are previously freed from the skin. It can be extracted both warm and cold. The kernels contain 50% to 60% oil.

use

In contrast to other vegetable oils, tung oil is not suitable for nutrition . It is mainly used for the production of varnish , partly also for the production of soap and linoleum , as a lubricating oil and as a binding agent in painting . It was also used to produce "lamp soot".

Raw wood (above) turns yellowish-golden after treatment with tung oil.

Tung oil polymerizes and oxidizes in a similar way to linseed oil , but dries faster and forms a resinous , hard, matt surface. In painting, there is a high risk of embrittlement or cracking when using tung oil alone. Therefore it is mostly used in a mixture with linseed oil varnish . When added up to 20% to the linseed oil varnish, it accelerates drying and reduces swelling caused by water. Mixed with linseed oil, it has a particularly good durability and weather resistance. When added in small quantities to the top coat of linseed oil paints without solvents, it increases their gloss and abrasion resistance.

In the electrical industry, electrical components are vaporized with tung oil to increase their water resistance.

Web links

literature

  • Sabine Krist, Gerhard Buchbauer, Carina Klausberger: Lexicon of vegetable fats and oils. Springer, 2008, ISBN 978-3-211-75606-5 , pp. 453-457.
  • PS Ku: For the direct determination of eleostearic acid in wood oil (tung oil). In: Journal for analytical chemistry . 120 (1-2), 1940, p. 37.
  • J. Greenfield: Lectures of the 1959 Short Course on Drying Oils. In: J. Amer. Oil Chem. Soc. 36, 1959, p. 565.
  • CL Franzke, Duong Tan Phuoc & E. Hollstein: On the fatty acid composition of the seeds of wild Vietnamese oil plants. In: European Journal of Lipid Science and Technology. 73 (10), 1971, 639-642, doi: 10.1002 / lipi.19710731016 .
  • Anna Schönemann, Wolfgang Frenzel, Achim Unger and Ernst Kenndler: An Investigation of the Fatty Acid Composition of New and Aged Tung Oil. In: Studies in Conservation. Vol. 51, No. 2, 2006, pp. 99-110, JSTOR 20619434 .

Individual evidence

  1. ↑ a b Ullmann's Food and Feed. Vol. 2, Wiley, 2017, ISBN 978-3-527-33990-7 , pp. 665, 727.
  2. ^ A b c d e P. H. List, L. Hörhammer: Hagers Handbook of Pharmaceutical Practice. Volume 7: Dosage forms and auxiliaries , Part B, Springer, 1977, ISBN 978-3-642-65823-5 , p. 172.
  3. ↑ a b c d e Sabine Krist.
  4. ↑ Ajit Kaur, Madhuka Roy, Krishnendu Kundu: Transesterification process optimization for tung oil methyl ester (Aleurites fordii) and characterization of fuel as a substitute for diesel. In: International Journal of Chemical Studies. 5 (6), 2017, pp. 632–638 online (PDF; 565 kB), at chemijournal.com, accessed on November 25, 2017.
  5. ↑ Nelson Zornitta, Willian Cézar Nadaleti et al .: Evaluation of the Tung's fruits as a possible source of sustainable energy. In: Acta Scientiarum. Technology. Maringá. 39 (4), 2017, pp. 487-493, doi : 10.4025 / actascitechnol.v39i4.29857 .
  6. ↑ H. Gnamm, K. Grafe et al.: Handbook of Gerbereichemie und Lederfabrikation. Third volume: Das Leder , 1st part, Springer, 1936, ISBN 978-3-7091-2211-2 , p. 362.
  7. ↑ E. Bames, A. Bömer et al.: Handbuch der Lebensmittelchemie. 4th volume, Springer, 1939, ISBN 978-3-642-88819-9 , p. 505.
  8. ^ A b Reinhard Lieberei, Wolfgang Franke, Christoph Reisdorff: Nutzpflanzenkunde. 7th edition, Thieme, 2007, ISBN 978-3-13-530407-6 , p. 430.
  9. ↑ W. Blaschek, Rudolf Hansel u. a .: Hager's Handbook of Pharmaceutical Practice. Volume 2: Drugs A – K , 5, edition, Springer, 1998, ISBN 978-3-642-63794-0 , pp. 62 f.
  10. ↑ Heinrich Boul, Ernst Dillan u. a .: Scientific publications from the Siemens group. Volume IV, Issue 2, Springer, 1925, ISBN 978-3-662-22753-4 , p. 285.
  11. ↑ Xin You Liu, Maria Cristina Timar, Anca Maria Varodi, Song Lin Yi: Tung Oil and Linseed Oil as Traditional Finishing Materials Important for Furniture Conservation. In: Pro Ligno. Vol. 11 No. 4, 2015, pp. 571-579, online (PDF; 680 kB), at proligno.ro, accessed on February 10, 2017.
  12. ↑ Yingxing Song, E-tu Zen Sun, Shinou-chuan Sun: Chinese Technology in the Seventeenth Century. Dover Publications, 1966, ISBN 0-486-29593-1 , p. 285.